Behavioral methods used in the study of long-chain polyunsaturated fatty acid nutrition in primate infants

Domains of behavior may be broadly categorized as sensory, motor, motivational and arousal, cognitive, and social. Differences in these domains occur because of changes in brain structure and function. Docosahexaenoic acid (DHA; 22:6-23) and arachidonic acid (AA; 20:4-26) are major structural components of the brain that decrease when diets deficient in the essential fatty acids (EFA) alpha-linolenic acid and linoleic acid are consumed. Early electrophysiologic and behavioral studies in EFA-deficient rodents showed behavioral effects attributable to lower-than-normal accumulation of DHA and AA in the brain. More recently, electrophysiologic and behavioral studies in EFA-deficient primate infants and analogous studies in human infants have been conducted. The human infants were fed formulas that could result in lower-than-optimal accumulation of long-chain polyunsaturated fatty acids (LCPUFAs) in the brain during critical periods of development. This article describes the behavioral methods that have been used to study primate infants. These methods may be unfamiliar to many physicians and nutritionists who wish to read and interpret the human studies. The behavioral outcomes that have been evaluated in LCPUFA studies represent only a fraction of those available in the behavioral sciences. Specific developmental domains have been studied less often than global development, even though studies of nonhuman primates deficient in EFAs suggest that the former provide more information that could help target the underlying mechanisms of action of LCPUFAs in the brain.